Functional　coatings　are　effective　for　improving　the　properties　of　devices.　The　development　of　thin-film-based　surface　acoustic　wave　(SAW)　devices　coated　with　piezoelectric　zinc　oxide　(ZnO)　thin　films　has　attracted　considerable　attention.　The　orientation　and　thickness　of　piezoelectric　films　will　affect　the　characteristics　of　SAW　devices.　In　this　research,　(100)　ZnO　films　were　combined　with　diamond　to　form　new　composite　SAW　substrates.　The　SAW　properties　of　(100)　ZnO　films　on　diamond　with　four　composite　structures,　namely,　interdigital　transducer　(IDT)/(100)ZnO/diamond,　(100)ZnO/IDT/diamond,　IDT/(100)ZnO/metal/diamond,　and　metal/　(100)ZnO/IDT/diamond　were　systematically　analyzed　and　some　excellent　SAW　properties　were　observed.　In　particular,　for　mode　1　of　(100)ZnO/IDT/diamond,　a　maximum　K2　of　5.85%　and　a　maximum　velocity　of　8857　m/s　were　obtained　at　a　minimum　film　thickness　ratio　of　h/λ　=　0.11.　Such　research　results　provide　a　predictable　theoretical　basis　for　the　further　application　of　such　substrates　in　high-velocity　SAW　devices.　©　MYU　K.K.